Method for working the ends of steel pipe by upsetting and pressing

Abstract

A method for working at least one end of a steel pipe by upsetting and pressing which comprises an external upset portion having an outer taper being shaped by upset forging, the portion then being pressed by an internal upset die so as to displace the outer taper to an internal upset portion having an inner taper and then internal upset forging being applied by the internal upset die, thereby forming accurately the length of the inner taper and the curvature of a starting point of the portion having the inner taper.

What is claimed is: 
     
       1. A method of working the ends of a steel pipe by external upset and internal upset forging, comprising: external upsetting for shaping a wall thickness A thickened at an external periphery of the ends of a steel pipe and further shaping an outer taper portion 4 gradually reduced from said wall thickness by employing a first mandrel 3A while holding said pipe by a first die 2A;   press-working for shaping an inner taper portion 5 by displacing said wall thickness A and the outer taper portion 4 to an inner side of side pipe by moving a second die 2B in an axial direction;   internal upsetting for thickening the wall thickness in a radially inward direction at an end of said pipe by inserting a second mandrel 3B into the steel pipe held by said second die 2B;   external upsetting for shaping the wall thickness A so as to be thickened radially outwardly at said end of said pipe and the taper portion 4 gradually reduced therefrom by inserting a mandrel 3C thereinto while holding said pipe by employing said second die 2B with an engraved pattern K at a desired position; and   press-working for shaping a taper portion 5 by displacing said wall thickness A and the taper portion 4 to an inner side of the pipe by moving the mandrel 2B in said axial direction such that said wall thickness A of said steel pipe is pressed into said engraved pattern K.   
     
     
       2. A method of working a metal pipe, comprising: a step of upsetting an end of a metal pipe such that said end becomes larger in wall thickness measured in a radial direction with an outer periphery of said pipe having a taper between said end and an un-upset portion of said pipe, said upsetting step being performed using a die having a first section, a second section and a tapered section therebetween, said first section having an inner diameter substantially equal to an outer diameter of said pipe and said second section having an inner diameter equal to a desired outer diameter of said end after said upsetting step, said upsetting step being further performed using a first mandrel having a first portion, a second portion and an axial end portion therebetween, said first portion having an outer diameter substantially equal to an internal diameter of said pipe, said upsetting being performed by positioning an outer periphery of said end of said pipe within said die and by moving said axial end portion of said first mandrel axially into contact with and deforming a free end of said pipe;   a step of radially inwardly pressing said end after said upsetting step is performed such that said taper on said outer periphery of said pipe is worked in a radially inward direction to form a taper on an inner periphery of said pipe between said end and said un-upset portion of said pipe, said pressing step being performed using said die, said die including an engraved pattern in said first section thereof, said engraved pattern comprising an annular recess in said first section, said recess having an axially extending section with a diameter greater than said diameter of said first section, said die having a second tapered section between said axially extending section of said recess and part of said first section, said recess being between said part of said first section and said second section, said pressing step being performed by positioning an outer periphery of said end of said pipe within said recess and deforming said end with said die, and   a second step of upsetting said end after said pressing step such that said end becomes larger in wall thickness measured in said radial direction with an inner periphery of said end having an inner diameter which is smaller than an inner diameter of said end after said pressing step, said second upsetting step being performed using said die and a second mandrel, said second mandrel having a first portion, a second portion and an axial end portion therebetween, said first portion of said second mandrel having a diameter less than said diameter of said first portion of said first mandrel, said second upsetting step being performed by positioning said outer periphery of said end of said pipe within said recess and moving said axial end portion of said second mandrel axially into contact with and deforming said free end of said pipe, whereby said end of said pipe after said second upsetting step has an outer diameter larger than the diameter of the un-upset portion of said pipe and an inner diameter less than the diameter of the un-upset portion of said pipe.   
     
     
       3. The method of claim 2, wherein after said second upsetting step an inner periphery of said end of said pipe is spaced further radially from an inner periphery of said un-upset portion of said pipe than an outer periphery of said end of said pipe is spaced radially from an outer periphery of said un-upset portion of said pipe. 
     
     
       4. The method of claim 2, wherein said second portion of said first mandrel has an outer diameter no greater than said inner diameter of said second section of said first die. 
     
     
       5. The method of claim 2, wherein said die is a split die. 
     
     
       6. The method of claim 2, wherein said axial end portion of said first mandrel extends perpendicularly to an outer periphery of said first portion of said first mandrel. 
     
     
       7. The method of claim 2, wherein said axial end portion of said second mandrel extends perpendicularly to an outer periphery of said first portion of said second mandrel. 
     
     
       8. The method of claim 2, wherein said metal pipe is a steel pipe. 
     
     
       9. The method of claim 8, wherein said steel pipe is heated to a temperature of about 1000 degrees centigrade to 1250 degrees centigrade prior to said first upsetting step. 
     
     
       10. A method of working a metal pipe, comprising: a step of upsetting an end of a metal pipe such that said end becomes larger in wall thickness measured in a radial direction with an outer periphery of said pipe having a taper between said end and an un-upset portion of said pipe, said upsetting step being performed using a first die having a first section, a second section and a tapered section therebetween, said first section having an inner diameter substantially equal to an outer diameter of said pipe and said second section having an inner diameter equal to a desired outer diameter of said end after said upsetting step, said upsetting step being further performed using a first mandrel having a first portion, a second portion and an axial end portion therebetween, sid first portion having an outer diameter substantially equal to an internal diameter of said pipe, said upsetting being performed by positioning an outer periphery of said end of said pipe within said first die and by moving said axial end portion of said first mandrel axially into contact with and deforming a free end of said pipe;   a step of radially inwardly pressing said end after said upsetting step such that said taper on said outer periphery of said pipe is worked in a radially inward direction to form a taper on an inner periphery of said pipe between said end and said un-upset portion of said pipe, said pressing step being performed using a second die having a first section, a second section and a tapered section therebetween, said first section of said second die having an inner diameter substantially equal to said inner diameter of said first section of said first die and said second section of said second die having an inner diameter less than said inner diameter of said second section of said first die, said tapered section of said second die having an axial length less than an axial length of said tapered section of said first die, said pressing step being performed by positioning said outer periphery of said end of said pipe within said second die and deforming said end with said second die; and   a second step of upsetting said end after said pressing step such that said end becomes larger in wall thickness measured in said radial direction with an inner periphery of said end having an inner diameter which is smaller than an inner diameter of said end after said pressing step, said second upsetting step being performed using said second die and a second mandrel, said second mandrel having a first portion, a second portion and an axial end portion therebetween, said first portion of said second mandrel having a diameter less than said diameter of said first portion of said first mandrel, said second upsetting step being performed by positioning said outer periphery of said end of said pipe within said second die and moving said axial end portion of said second mandrel axially into contact with and deforming said free end of said pipe, whereby said end of said pipe after said second upsetting step has an outer diameter larger than the outer diameter of the un-upset portion of said pipe and an inner diameter less than the inner diameter of the un-upset portion of said pipe.   
     
     
       11. The method of claim 10, wherein after said second upsetting step an inner periphery of said end of said pipe is spaced further radially from an inner periphery of said un-upset portion of said pipe than an outer periphery of said end of said pipe is spaced radially from an outer periphery of said un-upset portion of said pipe. 
     
     
       12. The method of claim 10, wherein said second portion of said first mandrel has an outer diameter no greater than said inner diameter of said second section of said first die. 
     
     
       13. The method of claim 10, wherein said first and second dies are split dies. 
     
     
       14. The method of claim 10, wherein said axial end portion of said first mandrel extends perpendicularly to an outer periphery of said first portion of said first mandrel. 
     
     
       15. The method of claim 10, wherein said axial end portion of said second mandrel extends perpendicularly to an outer periphery of said first portion of said second mandrel. 
     
     
       16. The method of claim 10, wherein said metal pipe is a steel pipe. 
     
     
       17. The method of claim 16, wherein said steel pipe is heated to temperature of about 1000 degrees centigrade to 1250 degrees centigrade prior to said first upsetting step.